/**
 * Slack inbound-webhook verification.
 *
 * The native channel replaces `createSlackAdapter`'s built-in HMAC
 * check with a self-contained verifier:
 *
 * 1. If the caller supplied a {@link SlackWebhookVerifier} (e.g.
 *    Connect's OIDC-based forwarder), delegate to it.
 * 2. Otherwise, recompute the Slack v0 HMAC and compare with
 *    `X-Slack-Signature`. Rejects requests older than five minutes to
 *    foil replay attacks.
 *
 * Returns the verified raw body string on success so the caller can
 * parse it without re-reading the request stream.
 */
/**
 * Caller-supplied inbound webhook verifier. Used as an alternative to
 * HMAC verification — e.g. Connect supplies a verifier that
 * authenticates Connect-forwarded webhooks with Vercel OIDC instead
 * of Slack's signing secret.
 *
 * Contract (matches the chat SDK's `SlackAdapterConfig.webhookVerifier`):
 *
 * - **Throw / reject** → the channel responds 401 to Slack.
 * - **Return a falsy value** (`null` / `undefined` / `false` / `""` /
 *   `0`) → the channel responds 401 to Slack. This lets verifiers
 *   signal rejection without throwing — e.g. Connect's `vercelOidc()`
 *   returns `null` on a failed OIDC check.
 * - **Return a truthy non-string value** → verification accepted.
 * - **Return a string** → verification accepted, and the string
 *   replaces the raw body for downstream parsing. Useful when the
 *   verifier canonicalizes or substitutes the verified payload.
 */
export type SlackWebhookVerifier = (request: Request, body: string) => unknown | Promise<unknown>;
export interface SlackVerifyOptions {
    readonly signingSecret: string | undefined;
    readonly webhookVerifier: SlackWebhookVerifier | undefined;
    /** Max allowed clock skew, in seconds. Defaults to 5 minutes. */
    readonly maxSkewSeconds?: number;
}
/**
 * Verifies an inbound Slack webhook and returns its raw body.
 *
 * Throws when neither a signing secret nor a custom verifier is
 * available, when signature/timestamp checks fail, or when the
 * caller-supplied verifier rejects.
 */
export declare function verifySlackRequest(request: Request, options: SlackVerifyOptions): Promise<string>;